Regenerate a Mind's system prompt

Rebuild the Mind's full system prompt from its current knowledge base (knowledge items, patterns, embeddings), replacing any manual edits. Runs synchronously and returns the new prompt; the same generator powers the product's "Generate All" action. Call it after adding knowledge with the Knowledge API, or to reset a customised prompt. The optional personaContextOverride is injected as a highest-priority steering brief (for example to diverge from a sibling persona or adjust age / family details) without touching the stored knowledge; context from the caller's own Audiences and the Mind's cohort profile is added automatically. A Mind allocated into an Audience keeps its assigned identity: its exact age, gender and race/ethnicity are supplied to the generator and enforced on the result (demographic header and the biography's own stated age), so neither the override nor the generator can change them. Only the Mind owner may call this; members and team collaborators get 403 Forbidden.